During a recording or live performance, musicians and singers often desire the freedom of being able to have their musical instrument or voice audio signals being connected to recording or amplification devices without the encumbrance of an electrical cable.
Analog wireless systems that transmit audio signals over radio frequencies have existed for many decades and have been a viable solution but they include many limitations. Analog transmission systems for audio signals typically have limited bandwidth and dynamic range. The analog transmission system also is susceptible to unwanted radio interference being heard through the audio system. With an analog system, as the radio frequency degrades, or interference occurs, the audio quality degrades.
Radio signals, whether for analog or digital audio systems, fade over distance and are susceptible to fades from reflections that can cause the radio signal to be of an insufficient level at a receiver's antenna. Professional wireless systems often utilize a space diversity design, in which two antennas are used, either with a switch to a single receiver or to two independent receivers, in order to improve the likelihood that at least one of the antennas or receivers will pick up the radio signal adequately. Further spatial diversity can be achieved by separating the two antennas further, which can be achieved with remote antennas connected via a coaxial cable of sufficient quality so as to not degrade the RF signal being picked up by the remote antennas.
In typical digital wireless systems, once the radio signal has degraded to a level in which the digital data is unreadable, the audio signal must be muted. If using an existing digital protocol such as Wi-Fi, the receiver can request the retransmission of the digital audio data. Unfortunately, latency (e.g., delay time) is introduced to allow time for the retransmission. In many cases, the latency associated with the wireless transmission of digital audio can be easily tolerated. For example, digitally transmitting audio that is being played from a recording can contain latency in the tens of milliseconds without being obvious to the listener.
On the other hand, performers of live music can tolerate only very low latency (e.g., 5 milliseconds or less) before the latency can negatively affect the performance and interaction of musicians. As a result, present techniques for the retransmission of digital audio are not a viable solution because of the amount of time required for retransmission. Unfortunately, as commonly occurs when the RF signal of the digital audio is not properly received in real time, whether it is out of range or due to interference, some portion of the digital audio signal is lost.